1. Field of the Invention
The invention relates to a wedge anchor, more particularly to one that can be driven quickly into a blind hole and that can ensure a stable securing effect.
2. Description of the Related Art
Referring to FIG. 1, a conventional wedge anchor 1 is shown to include a shank 11, a tubular expansion sleeve 12, a washer 13, and a nut fastener 14. The shank 11 has a threaded section 111, a neck section 112 extending forwardly and coaxially from one end of the threaded section 111, and having a diameter slightly smaller than that of the threaded section 111, and an expander section 113 extending fowardly and coaxially from one end of the neck section 112. The expander section 113 has a frusto conical configuration with a cross-section that gradually decreases along an axis of the shank 11 in a direction toward the threaded section 111. The expander section 113 further has a surface that forms an angle of less than 8xc2x0 with respect to the axis of the shank 11. The expansion sleeve 12 is shorter than the shank 11, is sleeved on the neck section 112, and is formed from two interconnected retaining plates 121 that encircle the neck section 112. Each retaining plate 121 is formed with a boss 122 that projects radially and outwardly with respect to the shank 11. The washer 13 is sleeved on the shank 11, and the nut fastener 14 engages the threaded section 111 of the shank 11.
With further reference to FIG. 2, in use, when mounting a bracket 10 on a wall 2, a blind hole 20, which has a diameter that corresponds to the outer diameter of the shank 11 when sleeved with the expansion sleeve 12, is initially drilled into the wall 2. Thereafter, with the expansion sleeve 12 disposed thereon, the shank 11 is driven into the blind hole 20 with the use of a mallet. By using a spanner to rotate the nut fastener 14 relative to the shank 11, a torque is generated so as to create a force for moving the shank 11 outwardly of the blind hole 20. At this time, movement of the shank 11 will cause the bosses 122 on the retaining plates 121 to engage the surface of the blind hole 20. Also, since an increasing cross-section of the expander section 113 extends into the expansion sleeve 12, the retaining plates 121 are forced by the expander section 113 to expand in a radial outward direction with respect to the shank 11 for engaging the surface of the blind hole 20. Subsequently, the nut fastener 14 and the washer 13 are removed from the shank 11, and the bracket 10 is disposed on the shank 11. The nut fastener 14 and the washer 13 are again provided on the shank 11 for locking tightly the bracket 10 against the wall 2.
Some of the drawbacks associated with the use of the aforesaid conventional wedge anchor 1 are as follows:
1. The surface of the expander section 113 of the shank 11 of the conventional wedge anchor 1 is smooth, and the expansion sleeve 12 is formed with only two retaining plates 121 having only two bosses 122. Thus, when the nut fastener 14 is rotated, since the shank 11 is not held firmly in the blind hole 20, it is possible that the shank 11 will rotate with the nut fastener 14 and will rotate idly inside the blind hole 20 due to inadequate gripping with the surface of the blind hole 20. In addition, friction between the expander section 113 and the expansion sleeve 12 is relatively small. As such, due to lack of engagement between the expander section 113 and the expansion sleeve 12, when the nut fastener 14 is rotated, there is also a possibility that the expansion sleeve 12 will rotate idly relative to the shank 11, thereby preventing expansion of the retaining plates 121.
2. As mentioned hereinbefore, the expansion sleeve 12 is formed from two interconnected retaining plates 121 that encircle the neck section 112 of the shank 11. Because the arc lengths of the retaining plates 121 are relatively long, the retaining plates 121 are undesirably rigid and do not expand easily in the radial outward direction of the shank 11. As such, the surface of the expander section 113 cannot be formed with an angle that is greater than 8xc2x0 with respect to the axis of the shank 11 since the larger angle will hinder expansion of the retaining plates 121. The smaller angle will result in a longer distance that is required to be traveled by the shank 11 or expanding the retaining plates 121. Thus, the conventional wedge anchor 1 takes up a relatively long amount of time for fixing on the wall 2.
3. Because a relatively long expander section 113 is needed to expand the retaining plates 121, the shank 11 has a relatively large material requirement, thereby resulting in increased costs. In addition, a relatively long length of the shank 11 projects from the wall 2 due to the relatively long distance traveled by the shank 11 when expanding the retaining plates 121. The relatively long projecting length of the shank 11 can hinder subsequent bracket mounting and locking operations.
Therefore, the object of the present invention is to provide a wedge anchor that can be driven quickly into a blind hole and that can ensure a stable securing effect.
According to the present invention, a wedge anchor includes a shank, a tubular expansion sleeve, and a nut fastener. The shank has a threaded section, a neck section extending forwardly and coaxially from one end of the threaded section, and having a diameter smaller than that of the threaded section, and an expander section extending forwardly and coaxially from one end of the neck section, and having a cross-section that gradually decreases along an axis of the shank in a direction toward the threaded section. The expansion sleeve is shorter than the shank and is sleeved on the neck section. The nut fastener engages the threaded section of the shank.
The expander section has a surface that forms an angle greater than 8xc2x0 with respect to the axis of the shank, and is further formed with a plurality of longitudinal ribs that project radially and outwardly, that extend along the axis of the shank, and that are angularly spaced apart from each other. The expansion sleeve is formed with a plurality of a axially extending silts for engaging the longitudinal ribs on the expander section when the expander section is extended into the expansion sleeve. The slits configure that expansion sleeve with an annular base strip portion and the more than two retaining plates, each having a base edge connected to the base strip portion, a pair of parallel lateral edges, and a curved distal edge that interconnects the lateral edges and that curves forwardly in a direction away from the base strip portion. The lateral edges of adjacent ones of the retaining plates confine the slits. The curved distal edges of the adjacent ones of the retaining plates cooperate to form entrances into the slits. Each of the retaining plates is formed with a boss that projects radially and outwardly with respect to the shank.